Bicycle frame



FIG. 1 is a side elevational view of a bicycle frame showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is an enlarged left rear perspective view thereof; and

FIG. 4 is a bottom plan view of FIG. 3.

The broken lines in FIGS. 1 and 2 are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a bicycle frame, as shown and described. 